Thermoset composite material and structural component and method of making the same from engineered recycled rubber powder

ABSTRACT

A thermoset composite material that my used in the fabrication of structural components including railroad ties comprise a substantially homogeneous blend of an amount of vulcanized rubber particles including a predetermined ratio of different particles sizes, and a thermoset elastomeric binding agent added to the vulcanized rubber particles. The blend may comprise about 30% to about 97% by weight of the vulcanized rubber particles, and the blend is subjected to compression molding at a predetermined temperature and pressure for a resident time period forming the composite material. The ratio of different rubber particle sizes is selected so that the composite material has a desired density or is within a range of desired densities.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/151,637, filed Jun. 2, 2011, which claims the benefit of U.S.Provisional Application No. 61/351,369 filed Jun. 4, 2010, andincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to composite materials used in thefabrication of structural components, and the methods of making suchcomposite materials. More specifically, embodiments of the inventionpertain to thermoset composite materials made from engineered recycledrubber powder.

Various processes and methods have been developed for comminutingdiscarded rubber articles, such as tires, wherein the discarded rubberarticles are reduced to sizes that can be reused in production of newrubber products. The particulate form of this rubber product is oftenreferred to as crumb rubber or rubber powder. Rubber comminutingprocesses and apparatus must overcome the high degree of elasticity ofrubber. Indeed, the grinding or sheering of rubber products at ambienttemperatures generates sufficient heat whereby the resultant rubberparticles that are relatively non-reactive. Moreover, such processesproduce a crumb rubber that includes larger and non-uniform particulatesizes. While the crumb rubber produced by these processes wasinexpensive and economical to use to fabricate new rubber products, thecrumb rubber could not be used to develop a “rubber-based” product. Thatis, the crumb rubber is essentially used as filler materials, becausethe rubber polymer could not be cross-linked with other polymers.

Indeed, crumb rubber has been used as a secondary ingredient intechnical compounds and products, and has not been used as the primarybase polymer to which the composite is formulated and other additivesand constituents are added too. Typical commercial loadings fortechnical materials have been in the range of 1% to 15%. In suchinstances crumb rubber is used as a non-technical filler to reduceoverall compound costs, and may detract from the technical properties ofthe base polymers. For example, adding more crumb rubber wouldeffectively reduce tensile strength of a composite material.

Due to its inability to bond chemically, some prior art composites havebeen formulated employing plastics as the base polymer and utilizedextruding molding technologies in order to encapsulate the crumb rubber.In addition, thermoplastic elastomers (TPE's) used in the past had poorchemical and heat resistance and low thermal stability. Such TPE's oftensoften or melt at elevated temperatures derogating the polymer chain,making the composite material unusable.

Other processes for comminuting rubber articles have been developedwhereby certain steps are thermally-controlled. That is, the temperatureof the rubber particles is controlled or maintained at sufficiently lowtemperatures so that the temperature of the rubber during processingdoes not rise above its glass transition temperature causing theinherent elastic properties to emerge. Such processes are able toproduce crumb rubber powder with much smaller particle sizes and moreuniform distribution of a particle size. In addition, the crumb rubberparticles may potentially be more reactive and capable of chemicalbonding with other polymers. However, to date processes, methods orapparatuses have not been developed to take advantage of this technologyto produce composite materials that are molded or configured to be usedas functional structural components.

Providing a composite material that includes as its base materialengineered recycled rubber particles that are used to fabricatestructural components such as railroad ties may be particularlyadvantageous. As developing countries build out their transportationinfrastructure in harsh climates (extreme heat/cold, moisture,UV/sunlight, insects, etc), longer lasting technical materials need tobe used in order to amortize upfront costs over longer periods forfinancing and to reduce the cost of maintenance. Such use of compositematerials can overcome difficulties of servicing tracks in remotelocations, and reduce waste disposal.

BRIEF DESCRIPTION OF THE INVENTION

An embodiment of the invention includes a thermoset composite materialthat incorporates engineered recycled rubber particles (ERRP) as a basepolymer and a primary component to which supplementary ingredients areadded to enhance and improve desired mechanical and physical properties.Typical loadings may include as much as 30% by weight of ERRP, or moreand typically loadings may range from 60% to 90%, blended with athermoset elastomeric binding agent. This blend is subjected tocompressive molding forces at predetermined pressures and temperaturesto form a thermoset composite material that can be used as a structuralcomponent such as a railroad tie.

Because the composite material employs ERRP as the technical basedpolymer, the ERRP represents the largest constituent per pound offinished composite. As certain additives are incorporated and compoundedin specific ways and at predetermined times in the process, theproperties of the composite are enhanced. Embodiments of the thermosetcomposite material will not only allow railroad ties to meet industryspecifications, but also allow installation using the same equipment andfastening devices currently in use to install conventional ties. Thethermoset composite material is made from recycled materials and may bemanufactured to qualify as a carbon offset when compared to otherrailroad tie materials such as wood, concrete, plastic and othercomposites.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram describing the process for making the thermosetcomposite material.

FIG. 2 is a top perspective view of a railroad crosstie comprising thethermoset composite material.

FIG. 3 is a bottom perspective view of the railroad crosstie in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the invention for a thermoset composite material may befabricated from a blend of recycled vulcanized crumb rubber powder, alsoreferred to as engineered recycled rubber powder (“ERRP”) and athermoset elastomeric binding agent. This blend is mixed to form ahomogeneous mixture of the components and then is molded undersufficient heat and pressure for a resident time to form a compositematerial. In one embodiment, the thermoset elastomeric binding agent isa non-vulcanized rubber (provided preferably in granulated form)combined with a “cure package”, which facilitates the vulcanization ofthe rubber when the blend is subjected to heat and pressure. In anotherembodiment, the blend may include the ERRP combined with a thermosetpolyurethane or polyurea resin, which is also subjected to heat andpressure to provide a thermoset composite material. In eitherembodiment, the molded composite material has the desired propertiessuch as density, tensile strength, hardness and bending stiffness toserve as a structural component such as a railroad crosstie.

The ERRP or vulcanized rubber particles may be produced from knownprocesses such as methods disclosed in U.S. Pat. Nos. 5,588,600;7,093,781; and, 7,108,207 for comminuting particle rubber, which arcincorporated herein by reference. Such methods include steps for coolingor freezing rubber particles at cryogenic temperatures, beforecomminuting the rubber. Such crumb rubber powder includes theabove-referenced ERRP and may also be referred to as cryogenicallygranulated rubber powder. This crumb rubber powder exhibits a uniquesurface suitable to interfacial adhesion and excellent mechanicalproperties when processed in forming a composite material. Indeed, theuse of this rubber powder may reduce the need for expensive modifiers.

The invention is also contemplated to cover any ERRP or vulcanizedrubber particles that are fabricated under thermally controlledconditions, such as controlling the temperature of the rubber materialduring grinding steps or other steps in a comminuting process. Thus, theterm “thermally-controlled granulated rubber” as used herein shall meanany vulcanized crumb rubber or rubber product in particulate form thatis fabricated under thermally controlled conditions such thattemperature of the rubber is maintained. below a predeterminedtemperature that may have a deleterious effect on the physical ormechanical characteristics of the rubber.

The non-vulcanized rubber component may be a scrap rubber formulated foruse in production of rubber products such as tires; however, the rubberis scrapped as a result of not meeting manufacturing specifications.This scrap rubber is also commonly referred to as “green rubber”. Whenusing the green rubber or nonvulcanized rubber, vulcanizing agents areadded to facilitate vulcanization of the nonvulcanized rubber. Thus, a“cure package” may be added to the blend, wherein the cure package maycomprise sulfur in combination with additives such as accelerators,activators such as zinc oxide, stearic acid, antidegradants and/orantioxidants. The “cure package” provides for cross-linking of thenon-vulcanized rubber (either natural rubber or styrenebutadiene rubber(SBR)) to stabilize the thermoset composite material.

In addition, a de-polymerized vulcanized rubber, also known asPyro-Black, which is typically produced by the de-polymerization ofscrap tires, may be added to either of the two embodiments of the blend.In an alternative embodiment, or alternatively to utilizing Pyro-Black,Carbon Black may be used. Carbon Black is a form of amorphous carbonthat also has a high surface-area-to-volume ratio.

Embodiments of the invention are set forth in the below Table I;however, the invention is not limited to these embodiments and mayinclude the components of the composition or blend at differentconcentrations or different concentration ranges:

TABLE I % % % lbs loading lbs loading lbs loading Scrap Green Rubber -157.5 70% 112.5 50% 67.5 30% SBR Base Recycled Engineered 45 20% 90 40%112.5 50% Rubber Powder Pyro-Black 18  8% 18  8% 18  8% Otheringredients 4.5  2% 4.5  2% 27 12% 225 100%  225 100%  225 100% As shown a blend is formulated including about 30% to about 70% byweight of the non-vulcanized scrap rubber; about 20% to about 50% byweight of the vulcanized recycled engineered powder; about 8% by weightof the Pyro-Black or Carbon Black; and, about 2% to about 12% by weightof other ingredients. The “other ingredients” include the abovementioned “cure package” including the sulfur, accelerators, activatorsetc. In addition, the “other ingredients” may include binding agentsand/or compatibilizers that are known to be used with recycled rubbercompounds in the manufacture of composite materials. About 1% to 5% byweight of the blend may comprise the “cure package” including sulfur andother additives depending on the ratio of green to crumb rubber used.

In addition to the foregoing components, a blowing agent may be added tothe mixture to control some end-product characteristics such aselasticity, hardness, tensil strength, compression, weight, etc. Knownblowing agents that may be used with the above-described rubbermaterials may be selected from a group of blowing agents known assulphohydrazides, which may decompose at temperatures lower relative tosome other blowing agents. The sulphohydrazides may have a decompositiontemperature of about 105° C. or higher, compared to azodicarbonamideswhich may have decomposition temperatures ranging from about 165° C. toabout 210° C. As described in more detail, the blowing agents may beintroduced into the homogeneous mixture before thevulcanization/compression molding stage of the described process/methodbegins.

The particle size of the vulcanized rubber powder and non-vulcanizedrubber may vary according to the desired mechanical or physicalproperties of thermoset composite material fabricated using the blend.When referring to a particle size the term “mesh” may be used to referto a sample of rubber particles having generally a single size ordiameter, or a range of sizes. For example, a sample or an amount ofrubber particles in which the particles have a 10 mesh size shall meanthat a percentage (typically 95%) of the particles for the given samplehas a diameter of 2 mm or less, or 95% of the particles will passthrough a 10 mesh sieve. When referring to a sample, or given amount ofrubber particles, having a range of mesh sizes shall it is meant that acertain percentage (typically 95%) of the rubber particles for thatsample are within the designated range. For example, a sample havingrubber particles in the range of −40 mesh to +60 mesh shall refer toparticle sizes wherein about 95% of the particles will pass through a 40mesh sieve, but also be retained by a 60 mesh sieve. In this example,the particles of the given sample would have a diameter from about 0.25mm (250 μm) to about 0.4 mm (400 μm).

The thermally-controlled granulated vulcanized rubber particles or ERRP,as compared to other crumb rubber products, have more chemically activesites making it more reactive, thereby, providing a level ofcross-linking between the rubber particles and other polymers possible.Accordingly, the size of the particles and distribution of a particlesize within a sample of the ERRP directly affects the cross-linkingcapabilities of the ERRP with other polymers, such as theabove-described thermoset elastomeric bonding agents.

It follows, that the particle size and particle size distribution of thevulcanized rubber particles has a direct effect on physical propertiesof the blend before the blend is cured, which effects the processing ofthe blend and/or curing process. For example, smaller particle size andparticle size distribution may increase the viscosity of the blend,which may increase an incorporation time during mixing to create thehomogenous blend. In addition, a larger particle size distribution mayresult in the blend, in an extruded or molded form, to shrink or swellmore than smaller particles, which will directly affect the amount ofthe blend used to mold and form structural component according tocertain dimensions and configurations. In addition, the particle sizeand size distribution directly affects the density of the finalcomposite material, which in turn affects other mechanical and physicalproperties of the thermoset composite material. For example, tensilestrength of the composite material increases as the number of smallerparticles increase; an increase in hardness is consistent with smallerparticles sizes and distributions; or, the percentage of elongation atbreak also increases with smaller particle sizes.

With respect to embodiments of the invention, the particle size for thevulcanized rubber particles for a given blend may range anywhere fromabout 10 mesh to about 140 mesh. That is the size for all of thevulcanized rubber particles for a selected amount of ERRP may be asingle size selected from the size range from 10 mesh (larger) through140 mesh (smaller). Alternatively, the size of all of the particles fora selected amount of ERRP may vary in size such that there are particlesthat are no larger than 10 mesh and no smaller than 140 mesh.Preferably, the particle size is in the range of about 10 mesh to about60 mesh, and more preferably form about 20 mesh to about 40 mesh.

in an embodiment, a selected amount of ERRP used in the blend may have apredetermined ratio of different sizes of the vulcanized rubberparticles. This ratio of different particle sizes may be selectedaccording to one or more desired physical or mechanical properties ofthe thermoset composite material, which properties may be dependent onthe function of the structural component fabricated from the thermosetcomposite material. By way of example, a railroad tie which requires ahigh degree of stiffness with good tensile strength properties may befabricated from a blend of the ERRP and the thermoset elastomericbinding agent and have a density ranging from 45 lb/ft³ to about 80 lb/ft³, and preferably a density ranging from 60 lb/ft³ to about 70 lb/ft³. A blend including the ERRP for such a structural component mayinclude a ratio of particles sizes of the ERRP as follows:

-   -   about 25% of the particles have a −20 mesh size (25% have an        average diameter of 707 microns or smaller);    -   about 25% of the particles have a −40 mesh to +60 mesh size (25%        have a diameter of 250 microns-400 microns); and,    -   about 50% of the particles having a −80 mesh size (25% having an        average diameter of 177 microns or smaller).        Such a blend of ERRP and the binding agent may produce a        thermoset composite material having a density that is at least        60 lbs/ft³.

In another example, the ratio of different sizes of particles mayinclude a higher content of larger particles to affect a physicalcharacteristic of the composite material. For example, an increase oflarger particle size distribution may allow for additional vibrationdamping, and the thermoset composite material may of have a density ofabout 45-50 lbs/ft³. Such a blend may include ERRP with a ratio ofparticle sizes including:

-   -   about 33% of the particles having a −20 mesh size (33% have an        average diameter of 707 microns or smaller); about 33% of the        particles of −40 mesh to +60 mesh size (33% have a diameter of        250 microns-400 microns); and,    -   about 33% of the particles have −80 mesh (33% having an average        diameter of 177 microns or smaller).

In yet another example, a desired amount of elasticity may necessary fora vertical structural component such as a marine piling, wherein thethermoset composite material may have a density of about 40-50 lbs/ft³.Such a blend may include ERRP with a ratio of particle sizes including:

-   -   about 40% of the particles having a −20 mesh size (40% have an        average diameter of 707 microns or smaller);    -   about 30% of the particles of −40 mesh to +60 mesh size (30%        have a diameter of 250 microns-400 microns); and,    -   about 30% of the particles have −80 mesh (33% having an average        diameter of 177 microns or smaller).

With respect to FIG. 1, there is shown a flow diagram that outlines amethod for making a thermoset composite material; or, the same may becharacterized as a method of fabricating a structural component from athermoset composite material. In a first step 10, each of the componentsincluding the ERRP and the binder, which may include non-vulcanizedrubber particles in combination with the above-referenced “cure package”is introduced into a mixer (preferably a high shear mixer).Alternatively, a polyurethane/polyurea binding agent may be mixed withthe ERRP instead of the non-vulcanized rubber and cure package. As knownto those skilled in the art, high shear mixers may have counter-rotatingrotors that may generate considerable heat during the mixing process;therefore, measures may be taken to maintain the temperature of themixture, or an interior of the high shear mixture, below temperatures atwhich vulcanization may occur. Typical temperatures fir high shearmixing may be controlled from 100° F. to 175° F.

In an alternative step 12, additives such as de-polymerized vulcanizedrubber, fillers, blowing agents, compatibilizers, etc., may beintroduced at this stage. Some examples of fillers may include recycledfibrous materials such as recycled currency or carpet, calciumcarbonate, MISTRON® monomix talc or MISTRON® vapor talc or a granulatedsilica. It is understood that such a granulated silica has not been usedany rubber formulation to date.

Again in reference to step 12 regarding introduction of a blowing agentinto the blend, the blowing agent may be added in an amount of about0.00% to 0.5%, and preferably 0.025% to about 0.5% of theblend/composite material when added. Blowing agents are known assubstances that may be mixed into a variety of materials, includingrubber materials, that undergo a controlled degradation, which liberatesinert gas under the temperatures and pressures of compression molding togenerate cellular structures within the composite matrix. The stage atwhich the blowing agent is introduced into the homogeneous mixture maydepend on the type of blowing agent used. For example, a blowing agentthat decomposes at lower temperatures, such as sulphohydrazines, may beintroduced to the homogeneous mixture prior to injection into thecompression molding/vulcanization stage. To that end, blowing agents,such as azodicarbonamides that decompose at higher temperatures may beintroduced earlier into the homogeneous mixture at the mixing stage.Introduction of the blowing agent into the high shear mixer may also bedictated by the mixing temperature. A sufficient amount of blowing agentshould be introduced in order to achieve the desired physical propertiesof the end product.

At step 14, the above-described blend is mixed in the high shear mixerto achieve a substantially or generally homogeneous mix of the rubberand binder components. The term homogeneous as used herein generallymeans that the mixture has the same proportions throughout a givensample or multiple samples of different proportion to create aconsistent mixture. With respect to the weights of the compositions orblends set forth in Table I above and the below described compositionsin Tables II-XII, the mixing step 14 may take 5-10 minutes, or possiblyshorter or longer depending on the volume or weight of the blend.Similar mixing parameters may be used with the embodiment of the blendincluding the polyurethane or polyurea.

With respect to step 16, the homogeneous mixture is introduced into oneor more molds of a compression molding apparatuses wherein the mixtureundergoes compressed molding at a predetermined temperature, apredetermined pressure and for a resident time period. Depending on thetype of structural component being manufactured a plurality of molds maybe provided that are dimensioned to form the desired structuralcomponents. For example, molds dimensioned to form railroad ties may beprovided wherein the railroad tie manufactured may be 7″×9″×102″ (or108″). In such a case, the homogeneous mixture may be subjected fromabout 1,000 psi to 4,500 psi for a resident time of about 6 minutes toabout 10 minutes at a temperature ranging from about 200° F. to about350° F. These cited parameters are provided by way of example, and oneskilled in the art will appreciate that these parameters may varyaccording to the dimensions of the structural component, according tothe other physical characteristics such as elasticity, stiffness,hardness, compression strength, etc. and/or the concentrations levels ofthe different components.

An additional step 18 is also referenced in FIG. 1, wherein thehomogeneous mixture undergoes extrusion during the delivery of thehomogeneous mixture from the high shear mixer to the compression moldingprocess. An extruder may deliver the mixture under pressure andtemperature in order to maintain the mixture at a desired viscosity fordelivery to the compression molding process. In addition, the extrusionmay also maintain the homogeneous characteristic of the mixture; and,the amount or quantity extruded must correspond to the physicaldimensions of the structural component to be fabricated. The extrusionmay take place at temperatures of about 325° F. to about 400° F. atpressures ranging from pout 750 psi to about 1500 psi.

At steps 20 and 22, a structural component developed from theabove-described method and blend is removed from the mold and allowed tocool. The component may be cooled to ambient room temperature. Finally,at step 24 quality assurance tests may be conducted on one or moresample structural components to determine if the component meets somepredetermined criteria or physical property profile to function for anintended purpose.

Sample Testing of ERRP and Non-Vulcanized SBR

Samples of a thermoset composition including the ERRP, non-vulcanizedrubber and a cure package were subjected to pressure and heat for aresident time and then tested to determine various mechanical orphysical properties. A control formulation was developed and includedthe following components as set forth below in Table II:

TABLE II Control Formulation SBR 1805 Off-Grade 212.5 phr¹ Zinc Oxide 5phr Stearic Acid 1 phr TMQ² 2 phr IPPD³ 2 phr CBTS⁴ 1.5 phr RMS⁵ 2 phrTBBS⁶ 1 phr PEG⁷ 3350 3 phr ¹parts per hundred rubber; ²trimethyldihydroquinoline (antioxidant) ³isopropyl phenyl phenylendiamine(antioxidant) ⁴cyclohexyl benzothiazole sulfenamide (accelerator)⁵rubber makers' sulfur (primary curative agent) ⁶tertiary butylbenzothiazole sulfenaminde (delayed accelerator)

The SBR 1805 is a styrene-butadiene non-vulcanized rubber that was usedin place of green or scrap rubber. In addition, the SBR was provided in¼″×¼″×4″ strips; however, the SBR may be added in granulated or powderform with a particulate size of about 30-80 mesh. The cure packageincluded zinc oxide, stearic acid and the above listed compounds, whichare typically found in vulcanizing cure packages. In order to evaluate,the affect of engineered recycled rubber powder in the test samples, thecontrol formulation did not include any ERRP. In comparison, testedsamples included ERRP at different concentrations and with differentsized particles. The ERRP was obtained from Liberty Tire Recycling whichhas a corporate headquarters located in Pittsburgh, Pa., and includedcryogenically granulated rubber powder.

The Control Formulation including the SBR and cure package was milledfor 7 minutes in a two roll mill at a maximum temperature of about 150°F., to form a “master-hatch” that was tested and used to create the testsamples including the ERRP. A control sample of the master-batch wasthen placed in a mold and subject to compression molding at 4,500 psifor 10 minutes at about 350° F. This control sample was tested tomeasure various physical properties including hardness (Shore DurometerA), tensile strength, and elongation percentage at break and tensilemodulus at different levels of elongation. The test results for theControl Formulation are provided in the below Table III:

TABLE III Durometer Shore A 65 Tensile Strength PSI 405.6 Elongation % @Break 126.9 10% Modulus PSI 74.3 25% Modulus PSI 120.7 50% Modulus PSI184.4 100% Modulus PSI 330.6 Density lbs/cu. ft. 71.9

As described above, ERRP was added to portions of the master-batch atdifferent concentrations and having different granular or particlesizes. ERRP, having particle sizes ranging from 10 mesh to 18 mesh(Table IV), was added to respective portions of the master-batch atconcentrations of 20% by weight, 40% by weight and 50% by weight; andERRP having particle sizes ranging from 1.0 mesh to 30 mesh (Table V)were added to respective portions of the master-batch at concentrationsof 20% by weight, 40% by weight and 50% by weight. In addition, ERRPhaving a distributed particulate size of 20 mesh (Table VI) was added torespective portions of the master-batch at concentrations of 20% byweight, 40% by weight and 50% by weight; and, ERRP having a distributedparticulate size of 30 mesh (Table VII) was added to respective portionsof the master-batch at concentrations of 20% by weight, 40% by weightand 50% by weight.

The ERRP was added to the master-batch of the Control Formulation duringmilling in a two roll miller, which milling was conducted for 7 minutesat a temperature of about 150° F. Then the test samples were placed inmolds and subjected to compression molding at a pressure of about 4,500psi at a temperature of about 350° F. for about 10 minutes. The sampleswere then tested to measure the above-described physical properties.These test results are provided in the below Tables IV-VII:

TABLE IV 10-18 Mesh ERRP % by wt. ERRP 20 40 50 Durometer Shore A 69 7579 Tensile Strength PSI 488.3 472.5 432.4 Elongation % @ Break 175.1156.3 147.6 10% Modulus PSI 84.1 89 84.3 25% Modulus PSI 133.1 142.9136.6 50% Modulus PSI 197.8 209.5 201.4 100% Modulus PSI 329.3 348 331.1Density lbs/cu. ft. 72.2 72.6 72.7

TABLE V 10-30 Mesh ERRP % by wt. ERRP 20 40 50 Durometer Shore A 68 7073 Tensile Strength PSI 471.8 478.2 506.9 Elongation % @ Break 165.6157.2 171.6 10% Modulus PSI 49.4 85 84.7 25% Modulus PSI 126 137.8 139.950% Modulus PSI 190.9 201.8 207.4 100% Modulus PSI 331.3 338.3 345.3Density lbs/cu. ft. 72.1 72.5 72.6

TABLE VI 20 Mesh ERRP % by wt. ERRP 20 40 50 Durometer Shore A 70 72 75Tensile Strength PSI 503.2 560.2 518.3 Elongation % @ Break 162.7 167.6155.3 10% Modulus PSI 84 92.9 91.4 25% Modulus PSI 137.8 150.3 148.7 50%Modulus PSI 205.1 223.3 220.9 100% Modulus PSI 351.3 382.2 372.1 Densitylbs/cu. ft. 72.2 72.6 72.9

TABLE VII 30 Mesh ERRP % by wt. ERRP 20 40 50 Durometer Shore A 71 73 74Tensile Strength PSI 538.2 557.7 625.3 Elongation % @ Break 168.9 161.6180.2 10% Modulus PSI 87.4 86.9 92.3 25% Modulus PSI 142.2 148.7 156.450% Modulus PSI 210.8 223.4 233.3 100% Modulus PSI 361.9 381.7 399.9Density lbs/cu. ft. 7.23 73 74In general, the addition of the ERRP enhanced the physical properties ofthe samples relative to the Control Formulation. The test results alsoshow that an optimum concentration be about 40% to about 50% by weightof the ERRP. In addition, the smaller particle size produced a betteroverall property profile. That is, the samples that included the 20 meshand 30 mesh particle size distributions as compared to the samples withlarger size particles or samples having the range of particle sizes,produced a better overall property profile.

A masterbatch of the Control Formulation (including the SBR and curepackage) was also prepared for mixing with ERRP and other additives suchas blowing agents and binding fillers. More specifically, fillersincluding MISTRON® monomix talc and VCAR 140 ground silica (a granulatedrecycled silica) were added to different samples; and, blowing agentsincluding as AZO (azodicarbonamide) blowing agent and an OBSH (oxybisbenzene sulfonyl hydrazide) blowing agent.

With respect to the use of the fillers as set forth in Tables VIII andIX, the control sample included 80% by weight of the masterbatch and 20%by weight of the respective fillers. With respect to the samplesincluding the ERRP with the filler, samples included 40% by weight ofthe masterbatch, 40% by weight of the ERRP and 20% by weight of therespective filler. Again four different particle sizes of the ERRPincluding samples having particles sizes ranging from 10-18 mesh and10-30 mesh. In addition, samples having a particle size distribution of20 mesh and 30 mesh were including in the testing.

With respect to the samples including the blowing agents set forth inTables X and XI, the control sample included 99.5% by weight of themasterbatch and 0.5% by weight of the blowing agent. The samples withthe ERRP included 59.5% by weight of the masterbatch, 40% by weight ofthe ERRP and 0.5% by weight of the blowing agent. Again, these samplesincluded the above-described ERRP particle sizes. All samples in whichthe tillers and blowing agents were added included the above-describedcryogenically granulated ERRP.

The samples were prepared as described above including milling theconstituents of a blend in a two roll miller for 7 minutes. The blendswere then placed in a mold and heated for 10 minutes at 350° F. and4,500 psi of pressure. The test results for the samples including thefillers are listed in Tables VIII and Tables IX; and, the test resultsfor the samples including the blowing agents are listed in Tables X andXI below:

TABLE VIII S501 (control) S502 S503 S504 S505 Concentration % by wt. SPSSBR Masterbatch 80 40 40 40 40 Mistron Mono Mix Talc 20 20 20 20 20 ERRP10-18 mesh 40 ERRP 10-30 mesh 40 ERRP 20 mesh 40 ERRP 30 mesh 40 TestResults Durometer Shore A 79 76 81 81 81 Tensile Strength 558.2 426.6492 465.5 426.7 Elongation @ break 84.4 41.6 50.7 47.6 46.8 100% Modulus0 0 0 0 0 Density lbs/cu ft 81.3 82.2 82.2 82.2 82.2

TABLE IX S601 (control) S602 S603 S604 S605 Concentration % by wt. SBRMasterbatch 80 40 40 40 40 VCAR 140 ground silica 20 20 20 20 20 ERRP10-18 mesh 40 ERRP 10-30 mesh 40 ERRP 20 mesh 40 ERRP 30 mesh 40 TestResults Durometer Shore A 79 77 72 75 77 Tensile Strength 530.8 395.4397.4 414.2 513.7 Elongation @ break 126.2 96.9 100.1 111.1 124.4 100%Modulus 462.1 0 399.6 417.5 466.7 Density lbs/cu ft 80.9 81.8 81.8 81.881.8

TABLE X S1001 (control) S1002 S1003 S1004 S1005 Concentration % by wt.SBR Masterbatch 99.5 59.5 59.5 59.5 59.5 OBSH Blowing Agent 0.5 0.5 0.50.5 0.5 ERRP 10-18 mesh 40 ERRP 10-30 mesh 40 ERRP 20 mesh 40 ERRP 30mesh 40 Test Results Durometer Shore A 55 65 66 70 66 Tensile Strength440.5 481.8 550.3 642.9 578.7 Elongation @ break 162.3 149.1 155.8 159.3145.6 100% Modulus 289.9 374.4 406.8 438.8 450.4 Density lbs/cu ft 7272.3 72.3 72.3 72.3

TABLE XI S1101 (control) S1102 S1103 S1104 S1105 Concentration % by wt.SBR Masterbatch 99.5 59.5 59.5 59.5 59.5 AZO blowing agent 0.5 0.5 0.50.5 0.5 ERRP 10-18 mesh 40 ERRP 10-30 mesh 40 ERRP 20 mesh 40 ERRP 30mesh 40 Test Results Durometer Shore A 73 67 73 70 63 Tensile Strength687.2 478.1 606.6 681 662 Elongation @ break 120.3 101.6 122.4 131.5128.5 100% Modulus 619.8 461 530.2 558.4 538.2 Density lbs/cu ft 72.272.6 72.6 72.6 72.6

Sample Testing of ERRP and Polyurethane

Samples of a blend including the ERRP and polyurethane were alsoformulated, molded and tested. More specifically, a blend of about 95%ERRP and about 5% polyurethane (Marchein Series 3800 urethanepre-polymer binder) was mixed in a laboratory Hobart ribbon blender forabout 3-5 minutes. The samples included cryogenically granulated ERRPwith particles sizes of 10-30 mesh range and 10-18 mesh range, as wellas samples including a 20 mesh and 30 mesh particle size distributions.Each sample blend was transferred by hand to a 4″×4″×½″ where it washeated for 6 minutes at 200° F. under 1,000 psi of pressure, which was amaximum amount of pressure attained with a non-hydraulic laboratorypress. The test results for these samples is listed below in Table XII:

TABLE XII Sample Rubber Mesh Tear Strength Tensile Density Number Size(lbs) Strength (psi) (lb/cu ft) A53-39A1 10-30 mesh 50 255 53.8 A53-39A210-30 mesh 52 297 56.1 A53-39B1 10-30 mesh 74 244 54.4 A53-39B2 10-30mesh 63 280 53.6 A53-39C1    20 mesh 57 256 54.4 A53-39C2    20 mesh 55265 52.0

It is noted that a 30 mesh ERRP particle size was tested using 5% byweight of the polyurethane; however, the sample did not remain intactafter the molding process. Another sample was tested using 10% by weightof the polyurethane as a binder. Mechanical properties testingdemonstrated a tear strength of 74 lbs, tensile strength @ break of 321psi and a density of 60.5 g/in³. In addition, samples including only3.8% of the polyurethane and 96.2% by weight of the ERRP using the 10-30mesh, 10-18 mesh and 20 mesh were tested. These samples demonstratedtear strengths ranging from 40 lbs to 62 lbs, and tensile strengthranging from 236 to 305 psi. The 20 mesh sample demonstrated the highesttest results including the 62 lbs tear strength and the 305 psi tensilestrength.

Given the above test results, the use of polyurethane or polyurea as abinder in amount of about 3-15% by weight, with compression moldingtaking place at about 1,000 psi to about 4,500 psi at about 250° F. fora resident time of about 10 minutes, will produce structural componentsthat will meet the mechanical properties required for various structuralcomponents, including but not limited to railroad ties. The amount ofthe polyurethane or poly⁻urea is preferable about 5% to about 10% byweight.

As mentioned above, a structural component that may be fabricated fromthe above-described thermoset composite material is a railroad tie. Therailroad tie should be manufactured according to the preferred AmericanRailway Engineering and Maintenance-of-Way Association (AREMA)standards. Accordingly, a typical railroad tie manufactured according toAREMA standard is 7″×9″×102″ (or 108″). Furthermore, a thermosetcomposite material fabricated as described above having a DurometerShore A of at least 80, a tensile strength of at least 250 psi and adensity of about 55 lbs/ft³ may be AREMA standards for railroad ties.

In an embodiment as shown in FIGS. 2 and 3 a railroad tie 30configuration has the two vertical sides 28A and 28B, a top side 34A, abottom side 34B, and opposing ends 26A and 26B. Both vertical sides 28Aand 28B and each end 26A and 26B will be provided with substantiallystraight vertical grooves 32 at a minimum depth of 3/16″. As measuredvertically from the railroad tie bottom side, grooves on both verticalsides and both ends will terminate at a point so as to provide at least1″ of thickness of full 9′×(102 or 108)″ surface area. Thisconfiguration allows for vertical ejection of the tie from thecompression mold.

In addition, grooves may be provided on the bottom side of the railroadtie configuration. Because of the molding technique (compressionmolding) used, the groove configuration on the bottom side may consistof chevrons 30 or grooves in the horizontal plane; however, the types ofdepressions, grooves or indentations on any side of the component may beas simple or complex depending on the molding techniques used. Themolded grooves 32 and chevrons 36 provide a structural interlock withthe railroad tie and road-bed crushed stone support ballast to therebyprevent longitudinal movement of a railroad tie and rail assembly.Alternate interlocking sidewall configurations are possible, such astire tread patterns, using hydraulically or pneumatically driven moldside-wall movement.

While the preferred embodiments of the present invention have been shownand described herein, it will be obvious that such embodiments areprovided by way of example only. Numerous variations, changes andsubstitutions will occur to those of skill in the art without departingfrom the invention herein. Accordingly, it is intended that theinvention be limited only by the spirit and scope of the appendedclaims.

What is claimed is:
 1. A thermoset composite material comprising:vulcanized recycled rubber particles; and, a polyurea binding agent. 2.The thermoset composite material of claim 1 further comprising agranulated silica filler material.
 3. The thermoset composite materialof claim 1 further comprising a fibrous filler material.
 4. Thethermoset composite material of claim 1 further comprising a fibrousfiller material and a granulated silica material.
 5. The thermosetcomposite material of claim 1 wherein the composite material of claim 1is subjected to compression molding at one or more temperatures rangingfrom about 200° F. to about 350° F.
 6. The thermoset composite materialof claim 1 wherein the composite material comprises about 30% to about50% by weight of the vulcanized recycled rubber particles.
 7. Thethermoset composite material of claim 6 wherein the composite materialcomprises about 3% to about 15% by weight of the polyurea binding agent.8. A thermoset composite material for a composite structural component,comprising: about 30% to about 50% by weight of vulcanized recycledrubber particles; about 3% to about 15% by weight of a polyurea bindingagent; a granulated silica material; and, a fibrous filler material, 9.The thermoset composite material of claim 8 wherein the compositematerial of claim 1 is subjected to compression molding at one or moretemperatures ranging from about 200° F. to about 350° F. to form thecomposite structural component.
 10. The thermoset composite material ofclaim 9 wherein the structural component is a railroad tie.
 11. Acomposite structural component, comprising: a blend of vulcanizedrecycled rubber particles and a polyurea binding agent having beensubjected to a compressive molding force at one or more temperaturesranging from about 200° F. to about 350° F.
 12. The composite structuralcomponent of claim 11 wherein the blend comprises a about 30% to about50% by weight of the vulcanized recycled rubber particles, and about 3%to about 15% by weight of the polyurea binding agent.
 13. The compositestructural component of claim 11 wherein the blend further comprises agranulated silica material.
 14. The composite structural component ofclaim 12 wherein the blend further comprises a fibrous filler material.15. The composite structural component of claim 12 wherein the blendfurther comprises a granulated silica material and a fibrous fillermaterial.
 16. The composite structural component of claim 15 wherein thehomogenous blend is subjected to compression molding at one or moretemperatures ranging from about 200° F. to about 350° F. to form thecomposite structural component.
 17. A method of fabricating a compositestructural component, comprising: mixing vulcanized recycled rubberparticles with a polyurea binding agent to form a mixture; placing themixture into a mold having a desired geometric configuration associatedwith the composite structural component; and, applying a compressivemolding force to the mixture in the mold at one or more temperaturesranging from about 200° F. to about 350° F. to form the compositestructural component.
 18. The method of claim 17 further comprisingmixing a granulated silica material with the vulcanized recycled rubberparticles and the polyurea binding agent.
 19. The method of claim 17further comprising mixing a fibrous filler material with the vulcanizedrecycled rubber particles and the polyurea binding agent.
 20. The methodof claim 17 further comprising mixing a granulated silica material and afibrous filler material with the vulcanized recycled rubber particlesand the thermoset polyurea binding agent.